The US defence secretary arrived in Afghanistan on an unannounced visit Thursday, dpa quoted an official as saying. "I can confirm that Secretary Leon Panetta is in Afghanistan and he is scheduled to meet with the US and NATO officials and Afghan counterparts," a spokesman for the NATO-led international forces told dpa. It is Panetta's fourth visit to Afghanistan, and comes a day after at least 41 people were killed in several incidents in the country. A suicide bomber in the southern province of Kandahar killed 23 people, while an alleged NATO airstrike killed 18 in the eastern province of Logar. Afghan officials said the victims in Logar included civilians, but NATO said only insurgents were killed. Panetta came to Kabul from New Delhi where he urged India to extend its training programme for Afghan troops.